Multistatic Radar Via An Array of Multifunctional Automotive Transceivers

ABSTRACT

A first multifunction radar transceiver comprises a first transmitter and a first receiver. The transmitter is operable to transmit a first radar burst. The receiver is operable to receive reflections of the first radar burst and reflections of a second radar burst transmitted by a second multifunction radar transceiver. The receiver is operable to generate, based on characteristics of the received reflections of the first radar burst and the received reflections of the second radar burst, a first scene representation. The receiver is operable demodulate the second radar burst to recover a second scene representation. The receiver is operable to combine the first scene representation and the second scene representation to generate a composite scene representation.

PRIORITY CLAIM

This application is a continuation of Ser. No. 15/142,926 filed on Apr.29, 2016, which claims priority to U.S. provisional patent application62/155,728 titled “Multistatic Radar via an Array of MultifunctionalAutomotive Transceivers” filed on May 1, 2015, each of which is herebyincorporated herein by reference.

INCORPORATION BY REFERENCE

The entirety of each of the following applications is herebyincorporated herein by reference:

U.S. provisional patent application 62/160,316 titled “ScalableArchitecture for an Automotive Radar System” filed on May 12, 2015;

U.S. provisional patent application 62/160,015 titled “Calibration of aMultifunctional Automotive Radar System” filed on May 12, 2015;

U.S. provisional patent application 62/154,840 titled “MultifunctionalAutomotive Radar” filed on Apr. 30, 2015;

U.S. patent application Ser. No. 15/142,935 titled “MultifunctionalAutomotive Radar” filed on Apr. 29, 2016;

U.S. provisional patent application 62/162,206 titled “Dynamic OFDMSymbol Shaping for Radar Applications” filed on May 15, 2015; and

U.S. provisional patent application 62/167,950 titled “Cooperative andCrowd-Sourced Multifunctional Automotive Radar” filed on May 29, 2015.

BACKGROUND

Limitations and disadvantages of conventional automotive radar systemsand methods will become apparent to one of skill in the art, throughcomparison of such approaches with some aspects of the present methodand system set forth in the remainder of this disclosure with referenceto the drawings.

BRIEF SUMMARY

Methods and systems are provided for multistatic radar via an array ofmultifunctional automotive transceivers, substantially as illustrated byand/or described in connection with at least one of the figures, as setforth more completely in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an automobile comprising a plurality of multifunctionalradar transceivers.

FIG. 2A shows an example architecture of a multifunctional radar systemof an automobile.

FIG. 2B shows an example implementation of a receiver system on chip(SoC) of a multifunctional radar transceiver of FIG. 2A.

FIG. 2C shows an example implementation of a transmitter system on chip(SoC) of a multifunctional radar transceiver of FIG. 2A.

FIGS. 3A and 3B show two example signal formats used by amultifunctional radar transceiver.

FIG. 4 shows an example antenna pattern of the multifunctional radartransceiver of FIG. 2.

FIGS. 5A and 5B illustrate benefits of multiple multifunction radartransceivers operating cooperatively.

FIG. 6 is a flowchart illustrating generation of scene representationusing a plurality of multifunctional radar transceivers.

FIG. 7 is a flowchart illustrating an example process for synchronizingthe clocks of two multifunctional radar receivers.

FIGS. 8A and 8B illustrate operation of a multifunction radartransceiver for achieving synthetic aperture.

DETAILED DESCRIPTION

FIG. 1 shows an automobile comprising a plurality of multifunctionalradar transceivers 102 (labeled with subscripts ‘1’ through ‘8’) of anautomobile 100 (e.g., a passenger vehicle licensed for use on publicroads). Although the example automobile 100 comprises eight transceivers102 for illustration, any number may be present. Each multifunctionalradar transceiver 102 has a corresponding receive antenna pattern 104and transmit antenna pattern 106 (for clarity of illustration, thetransmit and receive patterns are shown as the same, but they need notbe). As discussed in further detail in the remainder of this disclosure,the multifunctional radar transceivers 102 may perform: (1) a radarfunction, (2) a positioning function, and (3) a communication function.

The radar function comprises transmitting millimeter wave signals andprocessing the reflections/returns of such signals to detect thepresence of, identity of, direction of, distance to, and/or speed ofobjects in the environment surrounding the automobile 100 (the “scene”).

The positioning function comprises use of the same millimeter wavesignals used for the radar function to improve upon coarse positiondetermined through other mechanisms such as GPS.

The communication function comprises communicating data among themultifunction radar transceivers 102 using of the same millimeter wavesignals as are used for the radar function. Such data may include, forexample, pixel or voxel data (and time and position metadata) generatedusing the radar and positioning functions.

Through a combination of the radar function, the positioning function,and the communication function, the multifunctional radar transceivers102 ₁-102 ₈ are operable to generate a scene representation (e.g., 2Dpixel grid or 3D voxel grid) where the absolute time of capture of thescene representation and/or the absolute position of the pixels (2D) orvoxels (3D) in the scene representation are known.

The circuitry 110 represents other circuitry of the automobile 100 suchas one or more transceivers (e.g., cellular, Wi-Fi, Bluetooth, GPS,etc.), instrumentation (e.g., entertainment system, driverindicators/gauges, driver controls), sensors for safety systems, etc.The circuitry 110 may be communicatively coupled to the transceivers 102via a CANbus, for example. The circuitry 110 may be operable to processdata from the transceivers and take action (e.g., trigger driver alerts,transmit messages via one or more of its transceivers, trigger brakingor other safety systems, etc.) in response to such data. The circuitry110 may also generate data which it may pass to the transceiver(s) 102for communication to a remote transceiver 102 (e.g., that is mounted toanother automobile and/or to infrastructure such the road, sign post,stop-light, etc.) In an example implementation, the circuitry 110 maycomprise a cell phone that connects to an electronics system of theautomobile 100 via USB, Bluetooth, Wi-Fi, or any other suitableinterface and then the electronics system 110 of the automobile 100leverages the cellular transceiver of the circuitry 110 for connectingto a cellular network.

FIG. 2A shows an example architecture of a multifunctional radar systemof an automobile. The example multifunctional radar system 200 comprisesN multifunction radar transceivers 102, a bus controller 206, areference clock generator 214, data bus 212, and clock distribution bus216. For clarity of illustration, example implementation details areshown for only the N^(th) transceiver (102 _(N)), but the othertransceivers 102 ₁-102 _(N−1) may be the same. Each multifunctionalradar transceiver 102 _(n) (the subscript ‘n’ used here to genericallyrepresent each of the transceivers 102 ₁-102 _(N) individually)comprises a receive SoC 202 _(n), a transmit SoC 204 _(n), a pluralityof receive antenna elements 208 (labeled with subscripts 1 through 4,where four was chosen arbitrarily for illustration but any numbergreater than one may be used), and a plurality of transmit antennaelements 210 (labeled with subscripts 1 through 4, where four was chosenarbitrarily for illustration but any number greater than one may beused, and the number of transmit antenna elements need not match thenumber of receive antenna elements). In an example implementation, eachof the multifunctional radar transceivers 102 comprises one or more CMOSdies on a printed circuit board. In an example implementation, each ofthe receive SoCs 202 _(N), the transmit SoC 204 _(N), the bus controller206, and the reference clock generator 214 is a separately packaged CMOSintegrated circuit.

Each of the receive antenna elements 208 ₁-208 ₄ comprises, for example,a copper microstrip patch antenna on a printed circuit board (e.g., FR4,Duroid, or the like). Although four elements 208 are shown forillustration, any number may be used.

Each receive SoC 202 _(n) is operable to receive millimeter wave signals(e.g., in the 76 to 81 GHz band) via the antenna elements 208 ₁-208 ₄.The receive SoC 202 _(n) is operable to process received millimeter wavesignals for supporting the radar, positioning, and communicationfunctions. The receive SoC 202 _(n) is also operable to communicate overdata bus 212 and to synchronize its timing to a signal output byreference clock 214 onto clock distribution bus 216. Additional detailsof an example receive SoC 202 _(n) are described below with reference toFIG. 2B.

Each of the transmit antenna elements 210 comprises, for example, acopper microstrip patch antenna on a printed circuit board (e.g., FR4,Duroid, or the like). Although four elements 210 are shown forillustration, any number may be used.

The transmit SoC 204 _(n) is operable to transmit millimeter wavesignals (e.g., in the 76 to 81 GHz band) via the antenna elements 210₁-210 ₄. The transmit SoC 204 _(n) is operable to generate the signalsin such a manner as to support the radar, positioning, and communicationfunctions. The transmit SoC 204 _(n) is also operable to communicateover data bus 212 and to synchronize its timing to a signal output byreference clock 214 onto clock distribution bus 216. Additional detailsof an example transmit SoC 204 _(n) are described below with referenceto FIG. 2C.

The bus controller 206 is operable to relay data between the data bus212 interconnecting the multifunction radar transceivers 102 ₁-102 _(N)and a data bus of the automobile 100 (e.g., a CAN bus). The bus 212 may,for example, be a high speed serial bus and the bus controller 206,receive SoC 202 _(n), and transmit SoC 204 _(n) may each be operable toperform serialization and deserialization for communicating over the bus212.

The reference clock generator 212 comprises a crystal oscillator, phaselocked loop, and/or other circuitry for generating a signal to act as aphase reference for receive SoC 202 _(n) and transmit SoC 204 _(n). Inan example implementation, the frequency of the reference signal may berelatively low compared to the millimeter wave frequencies (e.g., on theorder of tens or hundreds of MHz), which may greatly relax the routingrequirements for the bus 216 as compared to trying to distribute areference signal in the 77 to 81 GHz range. In another exampleimplementation, the frequency of the reference signal may be the same asthe millimeter wave carrier frequency (e.g., it the range 77 to 81 GHz).

FIG. 2B shows an example implementation of a receiver system on chip(SoC) of the multifunctional radar transceiver of FIG. 2A. The examplereceive SoC 202 _(n) comprises a plurality (a number corresponding tothe number of receive antenna elements 208) of receive analog front ends(Rx AFEs) 252, a plurality of analog-to-digital converters (ADCs) 254,digital signal processing circuitry 256, data processing circuitry 264,bus controller circuitry 258, clock generation circuitry 260, andcontrol and memory circuitry 262.

Each of the Rx AFEs 252 is operable to process a millimeter wave signal(e.g., in the band from 76 to 81 GHz) from a respective one of theplurality of antenna elements 208. The processing may comprise, forexample, low noise amplification, filtering, and down-conversion so asto output a 1 to 5 GHz wide intermediate frequency or baseband signal.

Each of the ADCs 254 is operable to digitize the output of acorresponding one of the Rx AFEs 252. For example, each Rx AFE 252 maydownconvert a received 76 to 77 GHz band to a 1 GHz wide baseband signalwhich the corresponding ADC 254 may then digitize to generate a 1 GHzwide digital signal. As another example, each Rx AFE 252 may downconverta received 76 to 81 GHz band to a 5 GHz wide baseband signal which thecorresponding ADC 254 may then digitize to generate a 5 GHz wide digitalsignal 255.

The digital signal processing circuitry 256 is operable to process thedigitized signals from the plurality of ADCs 254 to recover informationconveyed by the received signals. Such information may be conveyed bycharacteristics (e.g., latency, Doppler shift, signal strength, etc.) ofthe received signals, as is the case in a conventional radar system,and/or may be data that was modulated onto the received signals.

The processing performed by the digital signal processing circuit 256may comprise, for example, channel estimation and equalization.

The processing performed by the digital signal processing circuit 256may, where the millimeter wave signals are modulated by a data signal,comprise demodulation. For example, the millimeter wave signalstransmitted by transceivers 102 may comprise bursts (or “chirps”) whoseamplitude is modulated relatively slowly as compared to the channelfrequency (e.g., a few MHz as compared to a channel frequency of 76-81GHz), and the digital signal processing circuitry 256 may be operable totrack the signal envelope to recover the data signal. As anotherexample, the millimeter wave signals transmitted by transceivers 102 maycomprise OFDM symbols and the digital signal processing circuit 256 maybe operable to demodulate the received signals using a discrete Fouriertransform. The digital signal processing circuit 256 may then beoperable to demap the modulated signal according to one or more symbolconstellations, deinterleave the demapped bits, and decode the demappedbits. The recovered bits may then be provided to the control and memorysubsystem 262 and/or output onto the bus 212.

The processing performed by the digital signal processing circuit 256may comprise beamforming. The beamforming may comprise time-domainbeamforming in which one or more sets of phase and amplitudecoefficients is applied to each of the signals 255 in the time domain.Alternatively, or additionally, the beamforming may comprisefrequency-domain beamforming in which the signals 255 are firsttransformed to the frequency domain (e.g., via a DFT) and then eachsubband (e.g., each OFDM bin or group of OFDM bins) is processed using acorresponding one or more beamforming matrices determined for thatsubband. In this manner, different subbands may be communicated on beamspointed in different directions.

The processing performed by the digital signal processing circuit 256may comprise spectral analysis of the received signals. The spectralanalysis may comprise, for example, mixing received signals with one ormore transmitted signals to generate a difference signal. The spectralanalysis may comprise, for example, performing a discrete Fouriertransform on received signals. The spectral analysis may be used to, forexample, determine Doppler shift of received signals and/or to generatespectral signatures of detected objects in the scene (i.e., objects offof which the received signals reflected.).

The processing performed by the digital signal processing circuit 256may comprise separating different transmitted signals (e.g., originatingfrom different ones of the transceivers 102 ₁-102 ₈). The may comprise,for example, correlating the received signals with different orthogonalcodes and/or pseudorandom sequences used by different ones of thetransceivers 102 ₁-102 ₈. Alternatively, or additionally, separatingdifferent transmitted signals (e.g., to determine which transceiver 102sent which signal) may comprise directly recovering a respectiveidentifier (e.g., a unique identifier such as a MAC address or similar)modulated onto each of the millimeter wave signals. The ability todistinguish which, if any, energy arrived from each transceivers 102₁-102 ₈ may be useful for performing the radar function, the positioningfunction, and the communication function of the transceivers 102 ₁-102₈. For the radar and positioning functions, for example, theidentification of which of transceivers 102 ₁-102 ₈ sent any particularreceived signal may be used for determining the position and angle fromwhich the signal was transmitted (since the different transceivers 102₁-102 ₈ are at different positions on the automobile 100), which may beused for determining precise distance to, and location of, objects inthe scene. For the communication function, for example, theidentification of which of transceivers 102 ₁-102 ₈ sent any particularreceived signal may be used in a manner similar to a “from” address inmany networking protocols.

The data processing circuitry 264 is operable to process data output bythe digital signal processing circuitry 256. Such processing maycomprise, for example, implementing algorithms to generate arepresentation of the scene detected using the radar function. Based onthe angle, strength, timing, spectral content, and/or othercharacteristics of the received signals, the data processing circuitry264 may generate a 2D pixel grid or 3D voxel grid. In an exampleimplementation, each pixel or voxel may indicate an absolute position towhich it corresponds (determined via the positioning function of themultifunction radar system), the strength of returns, if any, receivedfrom that location (determined via the radar function of themultifunction radar system), spectral content of returns, if any,received from that location, and/or time(s) at which returns werereceived from that location and/or at which the pixel or voxel data wasupdated.

The data processing circuitry 264 may also be operable to process datareceived from the data bus 212. For example, positioning information maybe received via the bus 212 (e.g., GPS coordinates from a GPS receiverof the vehicle 100) and combined with data recovered from the digitalprocessing circuitry 264 for performing the positioning function. Forexample, scene representations from other radar transceivers 102 may bereceived via the data bus 212 and the data processing circuitry 260 mayuse such scene(s) along with its scene generated from the output ofdigital signal processing circuitry 256 to generate a composite scenerepresentation. Such a representation may have the benefit of radarreturns arriving from multiple angles (i.e., “seeing” the object frommultiple perspectives since the various transceivers 102 are located ondifferent locations on the automobile).

The processing performed by data processing circuitry 264 of data outputby digital signal processing circuitry 256 may comprise, for example,preparing data for output onto the data bus 212. For example, a scenerepresentation generated from the output of the digital signalprocessing circuity 256 may be transmitted onto the data bus 212.

The bus controller circuitry 258 may be substantially similar to the buscontroller 206 described above.

The clock generation circuitry 260 is operable to generate a pluralityof timing signals that are synchronized to the timing signal receivedvia bus 216. The timing signals may comprise, for example: a localoscillator signal for direct downconversion of received millimeter wavesignals (e.g., in the 76 to 81 GHz range), a sampling clock for the ADCs254 (e.g., between 2 and 20 GHz), and one or more clocks for clockingthe digital processing circuitry 256, the bus controller 258, and thecontrol and memory subsystem 262.

The control portion of subsystem 262 is operable to manage operations ofthe receiver SoC 202 _(n) (e.g., implement a state machine and/or othercontrol logic that controls the configuration of the other components ofthe receive SoC 202 _(n)). The control portion of subsystem 262 may, forexample, configure beamforming matrices used by the digital signalprocessing circuitry 256. For example, the control portion of subsystem262 may determine that particular directions are of interest at a giventime and may configure the beamforming to point beams in thoseparticular directions. Particular directions may be of interest because,for example, it is desired to determine more information about objectslocated in that direction and/or to listen for communications from othertransceivers 102 that are likely to come from that direction. Directionsof interest may be determined based on, for example, data received viathe data bus, data carried in previously received millimeter wavesignals, and/or previously generated scene representations.

The memory portion of subsystem 262 is operable to store relativelylarge amounts (e.g., hundreds of megabits) of information of a varietyof forms. For example, beamforming matrices, an identifier of thetransceiver 102, scrambling codes, and messages received from (via databus 212) and/or to be communicated to (via data bus 212 and/or viamillimeter wave signals) other transceivers are just some examples ofthe information which may be stored in the memory and readily accessibleto the SOC 202 _(n).

FIG. 2C shows an example implementation of a transmitter system on chip(SoC) of the multifunctional radar transceiver of FIG. 2A. The exampletransmit SoC 204 _(n) comprises a plurality of transmit analog frontends (Tx AFEs) 272, a plurality of analog-to-digital converters (ADCs)254, digital signal processing circuitry 276, data processing circuitry284, bus controller circuitry 278, clock generation circuit 280, andcontrol and memory subsystem 282.

Each of the Tx AFEs 272 is operable to receive an analog baseband signalfrom a respective one of ADCs 274, upconvert the signal to a millimeterwave (e.g., a 1 GHz to 5 GHz wide signal in the band from 76 to 81 GHz),and amplify the millimeter wave signal for output to a respective one ofantenna elements 210 ₁-210 ₄.

Each of the ADCs 274 is operable to convert a digital signal 275 fromthe digital signal processing circuitry 276 to an analog representation.For example, each signal 275 may be a 1 GHz to 5 GHz wide basebandsignal.

The digital signal processing circuitry 276 is operable to process oneor more data streams from data processing circuitry 284 to generate aplurality (four in the example shown) of digital baseband signals 275.Processing performed by digital signal processing circuitry 276 maycomprise, for example, encoding, interleaving, bit-to-symbol mapping,frequency mapping (mapping of symbols to subbands), modulation (e.g.,using discrete Fourier transform and/or inverse discrete Fouriertransform) beamforming, and/or the like.

The processing performed by the digital signal processing circuit 276may comprise generating modulated signals 275 ₁-275 ₄ and/or generatinga data signal to be modulated onto a carrier. As an example of theformer case, the digital signal processing circuit 276 may output acontinuous wave signal, or a chirp whose amplitude is modulated by adata signal whose frequency is relatively low (e.g., a few MHz) ascompared to the channel frequency (e.g., between 76 GHz and 81 GHz). Asanother example of the former case, the digital signal processingcircuit 276 may output an OFDM signal. As an example of the latter case,the digital signal processing circuit 276 may output a relatively lowbandwidth data signal (e.g., a few MHz) which may modulate a millimeterwave chirp generated by the clock generator 280.

The processing performed by the digital signal processing circuit 276may comprise beamforming. The beamforming may comprise time-domainbeamforming and/or frequency-domain beamforming.

Data processing circuit 284 is operable to generate one or more datasignals for modulation onto the millimeter wave signals transmitted bythe SoC 204 _(n). The data signals may, for example, be read from memoryof the SoC 202 _(n) (e.g., an identifier of the module 102 _(n)) and/orgenerated algorithmically (e.g., timestamps generated based on a clockof the control portion of subsystem 282). Additionally, oralternatively, the data may be received from bus 212 via bus controller278. The data processing circuit 284 may packetize and/or otherwiseformat the data.

Bus controller 278 may be substantially similar to the bus controller206 described above.

Clock generation circuit 280 is operable to generate a plurality oftiming signals that are synchronized to the timing signal received viabus 216. The timing signals may comprise, for example: a localoscillator signal for upconversion of baseband signals to millimeterwave signals (e.g., in the 76 to 81 GHz range), a sampling clock for theDACs 274 (e.g., between 2 and 20 GHz), and one or more clocks forclocking the digital processing circuitry 276, the bus controller 278,and the control and memory subsystem 282.

The control portion of subsystem 282 is operable to manage operations ofthe receiver SoC 204 _(n) (e.g., implement a state machine and/or othercontrol logic that controls the configuration of the other components ofthe receive SoC 204 _(n)). The control portion of subsystem 282 may, forexample, configure beamforming matrices used by the digital signalprocessing circuitry 276. For example, the control portion of subsystem282 may determine that particular directions are of interest at a giventime and may configure the beamforming to point beams in thoseparticular directions. Particular directions may be of interest because,for example, it may be desirable to determine more information aboutobjects located in that direction and/or to listen for communicationsfrom other transceivers 102 that are likely to come from that direction.Directions of interest may be determined based on, for example, datareceived via the data bus 212, scene scanning algorithms, and/or thelike.

The memory portion of subsystem 282 is operable to store relativelylarge amounts (e.g., hundreds of megabits) of information of a varietyof forms. For example, beamforming matrices, and messages received from(via data bus 212 and/or millimeter wave signals) and/or to becommunicated to (via data bus 212 and/or modulated onto millimeter waveradar signals) other transceivers are just some examples of theinformation which may be stored in the memory and readily-accessible tothe SoC 204 _(n).

FIGS. 3A and 3B show two example signal formats used by amultifunctional radar transceiver. In FIG. 3A, the millimeter wavesignal (e.g., a continuous wave signal or series of frequency ramped“chirps”) is amplitude modulated by a relatively slowly varying datasignal. In FIG. 3B the millimeter wave signal is an OFDM signal which,for any given burst (frame) may transmit one or more of a plurality ofsubbands 504 (twenty-four subbands were chosen arbitrarily forillustration, any number may be used). Each of the subbands 504 ₁-5042 ₄may be a continuous wave or may be modulated by a data signal (e.g., aN-QAM symbol corresponding to log₂(N) bits of the data signal).Different subbands and/or groups of subbands may be allocated fordifferent purposes (e.g., some for radar, some for positioning, and somefor communication). Similarly, using frequency-domain beamforming,different subbands and/or groups of subbands may be pointed in differentdirections for detecting objects at different locations in the sceneand/or for transmitting the data signal in directions (e.g., pointed atdifferent reflection paths leading to different ones of the transceivers102 ₁-102 ₈).

Data modulated onto the millimeter wave signal may be forward errorcorrection encoded for robustness. Data modulated onto the millimeterwave signal may be scrambled or encrypted for security (e.g., to preventspoofing, sniffing of communications, etc.).

FIG. 4 shows an example antenna pattern of the multifunctional radartransceiver of FIG. 2. For example, for the radar function, lobes 402and 408 may be used for identifying objects that are relatively closeand off to the side of the transceiver 102 _(n), and the lobes 404 and406 may be used for looking further in the distance (e.g., in thedirection of travel of the automobile 100 or looking behind theautomobile 100). As another example, for the radar function, the lobes402 and 408 may receive returns from the nearby road surface and theDoppler of such returns may be used for calculating the speed of theautomobile 100. As another example, for the communication function,lobes 402 and 408 may be used for directly communicating with anothertransceiver 102 off to the side of the depicted transceiver 102 _(n) andlobes 404 and 406 may be used for communicating with other transceivers102 by bouncing the signals off of objects in the scene.

Although four beams/lobes are shown for illustration, themultifunctional radar transceivers are not limited to any particularnumber of beams/lobes. There may be different numbers of beams atdifferent times based on, for example, the number of objects and/orangles of objects it is determined necessary or desirable to identify ortrack at any given time. There may be different numbers of beams atdifferent times based on, for example, number and/or location of othertransceivers 102 with which it is necessary or desirable to communicateat any given time. Similarly, the directions of the beams may vary overtime. For example, the directionality of any one or more of the beams402, 404, 406, and 408 may change periodically, based on what isdetected in the scene, based on desired communication to be sent orreceived, and/or the like.

FIGS. 5A and 5B illustrate benefits of multiple multifunction radartransceivers operating cooperatively. In FIGS. 5A and 5B, transceiver102 _(n) transmits one or more millimeter wave signals represented byarrows 506 a, 508 a, and 510 a. Arrow 506 b represents a reflection ofsignal 506 a off of object 520. Arrow 508 b represents a reflection ofsignal 508 a off of object 520. Arrow 510 b represents a reflection ofsignal 510 a off of object 520. In an example implementation, arrows 506a, 508 a, and 510 a represent paths of a millimeter wave energytransmitted via a single lobe that covers a relatively wide range ofangles. In an example implementation, each of arrows 506 a, 508 a, and510 a represent millimeter wave energy transmitted via a plurality oflobes each of which covers a relatively narrow range of angles. In anexample implementation, the arrows 506 a, 508 a, and 510 a representmillimeter wave signals in three different subbands.

In FIG. 5B, transceiver 102 _(m) (‘m’ between 1 and 8 for the exampleimplementation of FIG. 1) transmits one or more millimeter wave signalsrepresented by arrows 512 a and 514 a. Arrow 512 b represents areflection of signal 512 a off of object 520. Arrow 514 b represents areflection of signal 514 a off of object 520. Comparison of FIGS. 5A and5B reveals some advantages of the use of multiple transceivers 102. Forexample, in FIG. 5A, energy represented by arrow 508 b is not receivedand thus does not contribute the knowledge gathered about object 520. InFIG. 5B, on the other hand, the energy represented by arrow 508 b isreceived by transceiver 102 _(m), and thus can provide information aboutthe position, speed, shape, size, and/or other characteristics of theobject 520. Similarly, as a result of the transceiver 102 _(m)transmitting the millimeter wave radar signals represented by arrows 512a and 514 a, reflections 512 b and 514 b provide additional informationabout object 520. Thus, for the radar function, the combination of twotransceivers 102 _(n) and 102 _(m) provides for greater collection ofreflected energy (improving SNR) as well as a wider angle “view” of theobject 520.

Furthermore, the configuration of FIG. 5B can take advantage of thecommunication function supported by the transceivers 102 ₁-102 ₈, asdescribed next with reference to FIG. 6.

In block 602, transceiver 102 _(n) receives, via reflection off ofobject 520, first bursts of millimeter wave signals represented byarrows 506 a and 514 a, and transceiver 102 _(m) receives, viareflection off of object 520, first bursts of millimeter wave signalsrepresented by arrows 508 a and 512 a.

In block 604, transceiver 102 _(n) generates a first scenerepresentation based on its received first bursts, and transceiver 102_(m) generates a second scene representation based on its received firstbursts.

In block 606, transceiver 102 _(n) modulates a data signal conveying thefirst scene representation onto a second burst of a microwave signalrepresented by arrow 508 a, and transceiver 102 _(m) transmits a secondburst of a millimeter wave signal represented by arrow 512 a.

In block 608, transceiver 102 _(m) receives the reflection of the secondburst and demodulates it to recover the first scene representation.

In block 610, transceiver 102 _(m) reconciles the locations of the twoscene representations so they can be combined. That is, since the fieldof view of the two transceivers is different and/or the two scenerepresentations were captured at slightly different times while theautomobile 100 was moving, the same pixel or voxel coordinate (e.g.,pixel (0,0) or voxel (0,0,0)) in the two scene representations may notcorrespond to the same absolute location. Accordingly, the locations ofthe two scene representations need to be reconciled before they can becombined into a composite scene representation. To use an analogy,combining the two scene representations without first reconciling theirpositions would result in “double vision.”

In block 612, the transceiver 102 _(m) performs weighted combining ofthe two scene representation. Such a combining may comprise, for eachpixel or voxel coordinate, determining a relative reliability of the twoscene representation and then combining the two pixels or voxelsproportional to their reliabilities to generate a single, compositepixel or voxel.

This process may continue indefinitely. For example, the second burstsof the signals may be used by transceiver 102 _(n) to generate a thirdscene representation and by transceiver 102 _(m) to generate a fourthscene representation. A third burst may then convey the fourth scenerepresentation to transceiver 102 _(m) which may then combine the thirdand fourth scene representation with each other and/or with thecomposite scene representation generated in block 612. And the thirdbursts may be used generate fifth and sixth scene representations, andso on such that the composite scene representation evolves over time.

In another example implementation, the transceiver 102 _(n) may transmita scene representation to the transceiver 102 _(m) only afteraggregating/averaging the scene representation over multiple receivedbursts. In other words, each of the first and second scenerepresentations may itself be a composite generated over time (which maycorrespond to some distance in the direction of travel when theautomobile 100 is moving), over a range of angles, and/or over a rangeof subbands.

Because each of transceiver 102 _(n) and 102 _(m) runs off its own clockgenerators 260 and 280, combining of scene representations from the twotransceivers 102 _(n) and 102 _(m) as described above may requiresynchronizing their respective clocks. An example process for suchsynchronizing, which takes advantage of the communication function ofthe transceivers 102, is described next with reference to FIG. 7.

FIG. 7 is a flowchart illustrating an example process for synchronizingthe clocks of two multifunctional radar receivers.

In block 702, an object suitable for bouncing a data-modulated radarsignal from transceiver 102 _(n) to transceiver 102 _(m) is determinedby transceiver 102 _(n) and transceiver 102 _(m). A suitable object isone off of which sufficiently strong reflections of a radar signaltransmitted by transceiver 102 _(n) can be received by transceiver 102_(m). In the example of FIG. 6, the object 520 is determined to be asuitable object.

In block 704 the transceiver 102 _(n) points transmit and receive lobesat object 520 and the transceiver 102 _(m) points transmit and receivelobes at object 520.

In block 706, the transceiver 102 _(n), using the reflectionsrepresented by arrow 506 b, determines the distance between it andobject 520. Similarly, the transceiver 102 _(m), using the reflectionsrepresented by arrow 512 b, determines the distance between it andobject 520. Given the distances, and the known relative positions of thetransceivers 102 _(n) and 102 _(m) on the vehicle 100, the angles to usefor communications between 102 _(n) and 102 _(m) off of object 520 canbe determined.

In block 708, transceiver 102 _(n) generates a data signal that carriesa representation (e.g., alphanumeric) of the current time according toits clock generator 260 and a representation of the determined distanceto object 520. The transceiver 102 _(n) then modulates this data signalonto a radar burst which is transmitted at the angle determined in block706.

In block 710 the modulated radar signal transmitted in block 708reflects off object 520 and is received at transceiver 102 _(m).

In block 712, transceiver 102 _(m) demodulates the received signal torecover the data signal carrying the timestamp and the distance fromtransceiver 102 _(n) to object 520.

In block 714, transceiver 102 _(m) determines the time of flight of thereceived burst based on the speed of propagation of the millimeter wavesignals and the distances between the object 520 and the transceivers102 _(n) and 102 _(m).

In block 716 transceiver 102 _(m) adjusts its clock to match the clock102 _(n) based on the received timestamp and the determined time offlight.

FIGS. 8A and 8B illustrate operation of a multifunction radartransceiver for achieving synthetic aperture.

In block 802 of FIG. 8A, a beamforming matrix of a transceiver 102 _(n)is configured to have one lobe pointing at the road in order to trackthe speed of the automobile 100, and an a second lobe pointing in adirection that is at least slightly different than the direction oftravel of the automobile 100. In FIG. 8B, the automobile 100 istraveling in the Y direction and the coverage area of the second lobespans an angle 824 in the XY plane. The coverage area of the second lobeat time T1 is bounded by 8201 and the coverage area of the second lobeat time T2 is bounded by 820 ₂.

In block 804, corresponding to time T1, the transceiver 102 _(n)receives reflections of the coverage area bounded by 820 ₁ and generatesa first scene representation from those reflections. The scenerepresentation is stored to memory of transceiver 102 _(n).

In block 806, corresponding to time T2, the transceiver 102 _(n)receives reflections of the coverage area bounded by 820 ₂ and generatesa second scene representation from those reflections. The scenerepresentation is stored to memory of transceiver 102 _(n).

In block 808, the average speed of the automobile 100 between times T1and T2 is determined from the returns received via the first lobe

In block 810, the average speed calculated in block 808 is used todetermine the distance, D1, traveled between times T1 and T2.

In block 812, the locations of the scene representations are reconciled(i.e., the distance D1 is accounted for) before combining to generate acomposite scene representation.

In accordance with an example implementation of this disclosure, anautomobile 100 comprises a plurality of multifunctional radartransceivers (e.g., 102 _(n) and 102 _(m)). Each of the transceivers isoperable to receive reflections of millimeter wave signals transmittedby itself and/or by another one or more of the transceivers and processthe received reflections to determine information about environmentsurrounding the automobile (e.g., to generate a scene representationsuch as a 2D pixel grid or 3D voxel grid along with metadata describingthe objects represented by the grid). A first of the transceivers isoperable to express the determined information as a data signal andmodulate the data onto a millimeter wave radar signal that it transmits.A second of the transceivers is operable to receive a reflection of themillimeter wave radar signal and demodulate it to recover the datasignal. The second transceiver is operable to reconcile a scenerepresentation contained in the data signal with its own scenerepresentation and combine the two representations to generate acomposite scene representation. Reconciling the two scenerepresentations may comprise determining the absolute positions of thetwo scene representations. Reconciling the two scene representations maycomprise synchronizing the two transceivers using synchronization datamodulated onto millimeter wave radar signals.

In accordance with an example implementation of this disclosure, a firstmultifunction radar transceiver (e.g., 102 _(N)) comprises a firsttransmitter (e.g., 202 _(N)) and a first receiver (e.g., 204 _(N)). Thetransmitter is operable to transmit a first radar burst. The receiver isoperable to receive reflections of the first radar burst and reflectionsof a second radar burst transmitted by a second multifunction radartransceiver. The receiver is operable to generate, based oncharacteristics of the received reflections of the first radar burst andthe received reflections of the second radar burst, a first scenerepresentation. The receiver is operable demodulate the second radarburst to recover a second scene representation. The receiver is operableto combine the first scene representation and the second scenerepresentation to generate a composite scene representation. Thereceiver may be operable to convey the composite scene representation tothe transmitter via a data bus (e.g., 212). The transmitter may beoperable to modulate the composite scene-representation onto a thirdradar burst. The first radar burst may comprise one or more OFDMsymbols. The receiver may be operable to determine relativereliabilities of the first scene representation and the second scenerepresentation. The combination of the first scene representation andthe second scene representation may involve a weighted combining whereweights used are based on the relative reliabilities of the first scenerepresentation and the second scene representation. The receiver may beoperable to demodulate the second radar burst to recover a timestampthat corresponds to the time the second radar burst was transmitted bythe second multifunction radar receiver. Clock generation circuitry ofthe first multifunction radar transceiver is calibrated using thetimestamp. The first multifunction radar transceiver and secondmultifunction radar transceiver are located at different locations on avehicle (e.g., 100). The first multifunction radar transceiver andsecond multifunction radar transceiver may be communicatively coupledvia a communication bus of the vehicle. The first multifunction radartransceiver may be operable to receive or generate data to becommunicated to the second multifunction transceiver. The firstmultifunction radar transceiver may be operable to send the data to thesecond multifunction transceiver via the data bus if the data has firstcharacteristics. The first multifunction radar transceiver may beoperable to modulate the data onto the first radar burst if the data hassecond characteristics. The characteristics may comprise one or both of:required bandwidth for communication of the data and required latencyfor communication of the data.

The present method and/or system may be realized in hardware, software,or a combination of hardware and software. The present methods and/orsystems may be realized in a centralized fashion in at least onecomputing system, or in a distributed fashion where different elementsare spread across several interconnected computing systems. Any kind ofcomputing system or other apparatus adapted for carrying out the methodsdescribed herein is suited. A typical combination of hardware andsoftware may be a general-purpose computing system with a program orother code that, when being loaded and executed, controls the computingsystem such that it carries out the methods described herein. Anothertypical implementation may comprise an application specific integratedcircuit or chip. Some implementations may comprise a non-transitorymachine-readable (e.g., computer readable) medium (e.g., FLASH drive,optical disk, magnetic storage disk, or the like) having stored thereonone or more lines of code executable by a machine, thereby causing themachine to perform processes as described herein.

While the present method and/or system has been described with referenceto certain implementations, it will be understood by those skilled inthe art that various changes may be made and equivalents may besubstituted without departing from the scope of the present methodand/or system. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the presentdisclosure without departing from its scope. Therefore, it is intendedthat the present method and/or system not be limited to the particularimplementations disclosed, but that the present method and/or systemwill include all implementations falling within the scope of theappended claims.

As utilized herein the terms “circuits” and “circuitry” refer tophysical electronic components (i.e. hardware) and any software and/orfirmware (“code”) which may configure the hardware, be executed by thehardware, and or otherwise be associated with the hardware. As usedherein, for example, a particular processor and memory may comprise afirst “circuit” when executing a first one or more lines of code and maycomprise a second “circuit” when executing a second one or more lines ofcode. As utilized herein, “and/or” means any one or more of the items inthe list joined by “and/or”. As an example, “x and/or y” means anyelement of the three-element set {(x), (y), (x, y)}. In other words, “xand/or y” means “one or both of x and y”. As another example, “x, y,and/or z” means any element of the seven-element set {(x), (y), (z), (x,y), (x, z), (y, z), (x, y, z)}. In other words, “x, y and/or z” means“one or more of x, y and z”. As utilized herein, the term “exemplary”means serving as a non-limiting example, instance, or illustration. Asutilized herein, the terms “e.g.,” and “for example” set off lists ofone or more non-limiting examples, instances, or illustrations. Asutilized herein, circuitry is “operable” to perform a function wheneverthe circuitry comprises the necessary hardware and code (if any isnecessary) to perform the function, regardless of whether performance ofthe function is disabled or not enabled (e.g., by a user-configurablesetting, factory trim, etc.). As used herein, “microwave” frequenciesrange from approximately 300 MHz to 300 GHz and “millimeter wave”frequencies range from approximately 30 GHz to 300 GHz. Thus, the“microwave” band includes the “millimeter wave” band.

What is claimed is:
 1. A system comprising: a first multifunction radartransceiver comprising a first transmitter and a first receiver,wherein: the transmitter is operable to transmit a first radar burst;the receiver is operable to: receive reflections of the first radarburst and reflections of a second radar burst transmitted by a secondmultifunction radar transceiver; generate, based on characteristics ofthe received reflections of the first radar burst and the receivedreflections of the second radar burst, a first scene representation;demodulate the second radar burst to recover a second scenerepresentation; and combine the first scene representation and thesecond scene representation to generate a composite scenerepresentation.